In assembling semiconductor devices, such as transistors, to a printed circuit or p.c. board, various mount constructions have been employed to hold transistors in an upright position on the board with the wire leads thereof inserted into corresponding openings in the board. After this mechanical attachment has been accomplished, the leads are soldered by wave soldering or other suitable processes so that the transistors are electrically and functionally connected to the p.c. board circuitry. While prior transistor support constructions have been generally satisfactory, new and improved carrier constructions and methods of assembly are needed to insure precise alignment and positioning of the transistors and the insertion of their leads into lead holes in the board manually or by automation without lead damage to effect mechanical connection so that they can be subsequently soldered to the board with optimized results. Furthermore, new and improved carrier constructions and methods are needed for precisely mounting transistors to circuit boards so that transistor leads will not contact the metallic housing in which the boards are installed and to position the transistors for effective heat sinking to the housing.